cpp/openttd-patchpack/source Files · src/core/bitmath_func.cpp

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PeterN

Feature: Industries with neutral stations (e.g. Oil Rig) only supply/accept cargo to/from their neutral station. (#7234)

This change is a controlled by a game setting, located under Environment ->
Industries which allows toggling the behaviour. It defaults to enabled.

"Company stations can serve industries with attached neutral stations"

When enabled, industries with attached neutral station (such as Oil Rigs) may
also be served by company-owned stations built nearby. This is the traditional
behaviour.

When disabled, these industries may only be served by their neutral station.
Any nearby company-owned stations won't be able to serve them, nor will the
neutral station serve anything else other than the industry.

/* $Id$ */

/*
 * This file is part of OpenTTD.
 * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
 * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
 */

/** @file bitmath_func.cpp Functions related to bit mathematics. */

#include "../stdafx.h"
#include "bitmath_func.hpp"

#include "../safeguards.h"

const uint8 _ffb_64[64] = {
	0,  0,  1,  0,  2,  0,  1,  0,
	3,  0,  1,  0,  2,  0,  1,  0,
	4,  0,  1,  0,  2,  0,  1,  0,
	3,  0,  1,  0,  2,  0,  1,  0,
	5,  0,  1,  0,  2,  0,  1,  0,
	3,  0,  1,  0,  2,  0,  1,  0,
	4,  0,  1,  0,  2,  0,  1,  0,
	3,  0,  1,  0,  2,  0,  1,  0,
};

/**
 * Search the first set bit in a 32 bit variable.
 *
 * This algorithm is a static implementation of a log
 * congruence search algorithm. It checks the first half
 * if there is a bit set search there further. And this
 * way further. If no bit is set return 0.
 *
 * @param x The value to search
 * @return The position of the first bit set
 */
uint8 FindFirstBit(uint32 x)
{
	if (x == 0) return 0;
	/* The macro FIND_FIRST_BIT is better to use when your x is
	  not more than 128. */

	uint8 pos = 0;

	if ((x & 0x0000ffff) == 0) { x >>= 16; pos += 16; }
	if ((x & 0x000000ff) == 0) { x >>= 8;  pos += 8;  }
	if ((x & 0x0000000f) == 0) { x >>= 4;  pos += 4;  }
	if ((x & 0x00000003) == 0) { x >>= 2;  pos += 2;  }
	if ((x & 0x00000001) == 0) { pos += 1; }

	return pos;
}

/**
 * Search the last set bit in a 64 bit variable.
 *
 * This algorithm is a static implementation of a log
 * congruence search algorithm. It checks the second half
 * if there is a bit set search there further. And this
 * way further. If no bit is set return 0.
 *
 * @param x The value to search
 * @return The position of the last bit set
 */
uint8 FindLastBit(uint64 x)
{
	if (x == 0) return 0;

	uint8 pos = 0;

	if ((x & 0xffffffff00000000ULL) != 0) { x >>= 32; pos += 32; }
	if ((x & 0x00000000ffff0000ULL) != 0) { x >>= 16; pos += 16; }
	if ((x & 0x000000000000ff00ULL) != 0) { x >>= 8;  pos += 8;  }
	if ((x & 0x00000000000000f0ULL) != 0) { x >>= 4;  pos += 4;  }
	if ((x & 0x000000000000000cULL) != 0) { x >>= 2;  pos += 2;  }
	if ((x & 0x0000000000000002ULL) != 0) { pos += 1; }

	return pos;
}